This invention relates generally to internal-combustion engines of piston type and cylinder assemblies thereof and more particularly to an internal-combustion engine cylinder assembly having a cylinder head and a cylinder liner and further provided with a reinforcing ring tightly fitted around the upper or cylinder-head-end part of the liner and having cooling liquid passages communicating with respective recesses grooved in the outer cylindrical surface of the liner to form cooling liquid passageways of a cooling system.
As the output power of piston-type internal-combustion engines increases as in recent years, the temperatures of sliding parts of the engine such as those of the piston and cylinder liner become ever higher, and the temperature of the lubricating oil interposed between the piston rings and the cylinder also becomes higher, whereby it has become increasingly difficult to form a lubricating oil film between such sliding parts. One obvious solution of this problem is to provide ample cooling of the cylinder liner, but this is difficult to achieve with a conventional cylinder assembly of the type comprising a cylinder liner and a cylinder jacket encompassing the cylinder liner with a space formed therebetween for passage of a cooling liquid as described more fully hereinafter.
In another conventional type of cylinder assembly, numerous cooling liquid passageways are formed in the upper part of the cylinder liner, which in this upper part has a relatively large outer diameter and thus has a greater wall thickness than the lower or skirt part thereof. The liquid passageways, however, lower the mechanical strength of the linear and give rise to cracks therein in some instances. To overcome this problem, the outer diameter of the outer part of the liner can be increased, but this measure would make the cylinder structure bulky and increase the material cost.